OAKLAND — The A’s have already done some improbable things this season, but there is always room for improvement as Oakland showed in a supersized 3-2 18-inning victory over New York, completing a three-game sweep of the Yankees.

The game-winning hit went to rookie Nate Freiman, he of two career hits against right-handed pitching. It came off Mariano Rivera, he of the express lane to Cooperstown with his 631 career saves.

And the pitching victory went to Jesse Chavez, who started the year in Triple-A but who threw 5﻿2/3 shutout innings Thursday, including retiring the final 13 men he faced.

These aren’t necessarily guys who are on anybody’s radar at the MLB Network or “SportsCenter,” but they are players who have made, and who continue to make, contributions to one of the most entertaining stories in baseball.

And there are enough players in A’s uniforms performing similarly well that Oakland is 14 games over .500, in first place in the American League West and winner of 21 of its last 26 games.

The A’s had already played a franchise-record six-hour, 32-minute game that lasted 19 innings against the Angels back on April 29. Oakland won that one, but at a cost — Coco Crisp, Chris Young and Brett Anderson all went on the disabled list following that game.

This game doesn’t seem to have exacted that level of toll, but Josh Donaldson came out of the game in the 15th inning with a leg cramp. His replacement was one Nathan Samuel Freiman, who grew up reviling the Yankees and loving the Red Sox.

Rivera walked Jed Lowrie with men on first and third and one out in the 18th for the express purpose of getting to Freiman. The matchup should have been completely one-sided. It was, just not the way the Yankees expected.

“I saw (the at-bat) coming. I thought they would walk Jed to get to me,” Freiman said. “I haven’t faced a lot of right-handers (2-for-24, a .083 average). I was a Red Sox fan, but I always rooted for him, what he’s done, the way he’s always carried himself.”

Freiman hacked at a Rivera cutter, broke his bat on the pitch but drove it over the infield. John Jaso scored from third and the partying began.

The A’s gave Freiman the obligatory-at-this-point pie in the face — actually two pies from Josh Reddick, and a Gatorade bath.

“I didn’t know that that was a thing now,” Freiman said. “The pie I was sort of expecting, but not the bath.”

Chavez didn’t get a pie, but he surely deserved one. He was the last available pitcher, with the A’s unwilling to use overworked lefty Sean Doolittle, so he took over with two on and one out in the 13th inning from Hideki Okajima, registered two quick strikeouts, then went a total of 5﻿2/3 innings, during which he allowed one hit, two walks (one intentional) and retired the final 13 batters he faced.

The A’s were willing to stretch him out in part because he was starting at Triple-A Sacramento before the A’s called him up to fill a bullpen job and in part because Friday starter Tommy Milone was the next pitcher in line should Chavez fail.

“I told myself I was in it for the long haul,” Chavez said. “I knew eventually we’d be able to score. I wanted to tell them I’d go until we won.”

For whatever reason, the A’s usually do. They have won 10 of their last 13, 16 of their last 20 and 21 of their last 26. That’s a whole mess of winning.

“This is the kind of thing that brings a club together,” Freiman said.

At this moment, the A’s seem to be about as together as any team in the major leagues.

Donaldson said he developed leg cramps in the top of the 15th inning. When the third baseman was taken out of the game, Brandon Moss moved to third for the second time in his big league career and Freiman took over for Moss at first. “Tomorrow is for (the trainer) to say,” Donaldson said when asked about his availability for Friday.

Jaso, serving as D.H., fouled a ball off his shin and was limping for the final innings. And catcher Derek Norris caught 18 innings.

With his ailing foot, Crisp wasn’t going to be allowed to bat until a hit would score a run, manager Bob Melvin said. He pinch-hit in the 15th with Moss at second base and singled, only to see Moss thrown out at the plate on some nice defensive work from the Yankees. Crisp remained in the game and singled again in his only other at-bat.

Looking at his lineup for Friday’s series opener against Seattle, Melvin said some of his guys were close to delirious by game’s end. “I’m pretty sure I have nine D.H.’s for tomorrow,” the manager said.

Jarrod Parker made one of his best starts of the season, going a season-best eight innings while allowing two runs, both of those on a first-inning Robinson Cano homer. Parker didn’t allow a run in his last seven innings, and the bullpen threw 10 scoreless innings.

John Hickey is a sports reporter for the Bay Area News Group who returned to the organization in 2013 to cover the A's, a team he'd covered previously from 1986-1999. In between he covered the Mariners in Seattle for 13 seasons.

A long-awaited plan to keep the Raiders in Oakland was unveiled late Friday by city and Alameda County officials. In a news release issued late Friday afternoon, local officials touted the plan for a new $1.3 billion stadium and mixed-use development designed to keep the team at the Coliseum site. Raiders owner Mark Davis currently is pursuing a plan to...